1. Field of the Invention
The present invention relates to a method and apparatus for cutting coated sheets. Specifically, the present invention relates to a method and apparatus for cutting coated sheets by passing the coated sheets between opposing discoid cutting blades.
2. Description of the Related Art
Conventionally, there has been known a coated sheet that comprises a sheet substrate such as of paper, film, or resin-coated paper; and a coating layer formed on the sheet substrate, wherein the coating layer is filled with fine particles of silica or the like held together by a resin binder. Such a coated sheet is formed as a web through the steps of applying a liquid coating material to a long substrate, drying the coated substrate, and winding the dried substrate in a roll form. The web so obtained is then cut to a desired size by cutting the web in the web feed direction and/or cutting it in the cross web direction, i.e., the direction perpendicular to the web feed direction, while being unwound from the rolled web. After that, these cut sheets are brought to market as a final manufactured product such as information recording paper or the like. Typically, shear-cutting techniques are used for cutting such a web in its feed direction. In a shear cutting technique, the web of coated sheet is shear-cut by rotating a disk-shaped upper cutting blade having a keen or sharp knife angle and a disk-shaped lower cutting blade having a substantially right knife angle, while the coated sheet is passed through between the upper and lower cutting blade (for example, see Japanese Patent Publication No. 2001-260077).
However, as a variety of materials have been used upon request for manufacturing coated sheets in various manners, it becomes more difficult to select appropriate cutting conditions for shear-cutting the coated sheet while pulling out the coated sheet wound in a roll form, in the feed direction. If the cutting conditions are not properly selected, there arises a problem that cracks and/or flaws may be produced in the coating layer near the cut edges of the sheet. Especially, when the coating layer is hard and fragile, the aforementioned cracks and/or flaws could be conspicuously produced in the coating layer.